1. Field of the Invention
The present invention relates to athletic mouthguards and dental appliances, and specifically to self-customizable mouthguards and dental appliances.
2. Description of Related Art
It is known that mouthguards have been used to protect athletes in contact sports from injury to the teeth and also to protect the temporomandibular joint from destructive forces. Recent evidence also indicates that mouthguards may be beneficial in minimizing or preventing concussion. Performance of mouthguards is described in Elkin, M., Increased Athletic Performance using Mouthguards—True or False?, J. New Jersey Dental Assoc., 1996; Stenger, J. M., Mouthguards protection against shock to the head, neck and teeth, J. Am. Dental Assoc., 1964; Duda, M., Which Athletes Should Wear Mouthguards?, Phys. and Sports Med., 1987; and Hickey, J. C., The Relation of mouth protectors to cranial pressure and deformation, J. Am. Dental Assoc., 1967.
Athletes tend to clench their teeth upon exertion. This clenching creates considerable forces on the upper and lower jaws and can lead to damage to the teeth, headaches, neck pain and injury to the temporomandibular joint. Therefore, dental appliances and/or mouthguards have been created to place pads between the upper and lower dentition to prevent this clenching and possible damage to the teeth and other structures.
Historically, mouthguards have been made of ethylene vinyl acetate (EVA). Due to the user clenching and chewing on the appliance, it is subject to degradation. EVA is translucent or white and cannot be made clear. EVA also has a mild ester-like odor and will degrade to hazardous vinyl acetate, acetic acid, carbon monoxide and hazardous hydrocarbon oxidation products. While the mechanical and physical properties of EVA generally fulfill the safety requirements for a custom fitted mouthguard, attempts to mass-produce EVA as a Boil-and-Bite, “do-it-yourself” mouthguard have had limited success and acceptance (see Bishop, B. M., Davis, E. H., von Fraunhoffer, J. A., “Materials for mouth protectors” J. Prosthet. Dent. 1985; 53:256-61 and Chalmers, D. J., “Mouthguards: Protection for mouth in the rugby union” Sports Med. 1998; 25(5):339-49; Winters, Sr., J. E. “Role of properly fitted mouthguards in prevention of sport-related Concussion” J. Athletic Training 2001; 36(3): 339-341). These mouthguards do not fit well and their poor retention plus their lack of proper extension into the buccal vestibule have led Park et al. to state unless dramatic improvements are made, they should not be promoted to customers as they are now (see Park, J. B., Shaull, K. L., Overton, B., Donly, K. I., “Improving mouthguard” J. Prosthe.t Dent. 1994; 72: 373-80.
Currently, commercially available mouthguards are (arbitrarily) classified as:                1. Stock over-the-counter—one size fits all. They must be held in place by clenching the teeth together—an obvious contraindication for continuous, vigorous sports requiring unobstructed airways.        2. Boil-and-Bite, mouth formed—these are placed in boiling water and then fitted into the mouth. When athletes attempt to fit these mouthguards, the resulting fit is often inadequate, loose and uncomfortable (see American Society for Testing and Materials. Standard practice for care and use of mouthguards (F 687-80). Reapproved 1992. Philadelphia (PA): American Society for Testing and Materials, 1992).        
Attempts been made in engineering EVA for a better fit, comfort and protection; these include sophisticated multilayer composites with a different softening temperature, custom gel fit liner, grip fit technology, or blending EVA with various polymers such as Kraton and polyurethane. (See Kittelsen et al., “Quadruple composite performance enhancing mouthguard (U.S. Pat. No. 6,675,807); Wagner, E. C. “Custom fit mouthguard” (U.S. Pat. No. 5,566,684); Gel Max Shock Doctor's Mouthguard. www.shockdoc.com; Shock Doctor's 7001 V3.0 Mouthguard. www.shockdoc.com; Shock Doctor's V3 Mouthguard. www.shockdoc.com); and Brett et al., “Mouthguard and method of making” U.S. Pat. No. 6,584,978.). Despite these efforts, comfortable custom fitted mouthguards are still difficult to achieve and many athletic trainers and sports participants still prefer the custom-fabricated mouthguards, i.e. from dentist made study casts of the teeth. They are comfortable, fit better with good retention, and allow the user to breathe and speak more easily. Despite the cost, experts in the medical, dental and sports professions are still recommending the custom fitted mouthguard as the best choice and protection (see Chalmers, D. J., “Mouthguards: Protection for mouth in the rugby union” Sports Med. 1998; 25(5):339-49; Winters, Sr., J. E. “Role of properly fitted mouthguards in prevention of sport-related Concussion” J. Athletic Training 2001; 36(3): 339-341).
FIG. 1 illustrates a conventional noncustom mouthguard 10 which generally includes a horseshoe or u-shaped base or occlusal pad 11 with a lingual wall 12 and a labial wall 13.
U.S. Pat. No. 6,491,036 discloses a low density polyethylene dental appliance and mouthguard including a nucleating agent. A suitable material is EXACT® from ExxonMobil Chemical Company of Houston, Tex. 77253-3272. This material has ethylene crystallinity which produces a non-elastomeric material with little flexibility or no shrinkage.
There is a need for mouthguards and dental appliances of custom fit without the need to have it formed by a dentist. There is a need for self-customizing dental appliance or mouthguard which is aesthetic, offers protection for the teeth, exhibiting strong tensile strength, high impact properties, flexibility, and have little or no odor.